High-voltage analog switch circuit is used in various devices including a Diagnostic Ultrasound System as an example. In the case of using a high-voltage analog switch circuit in a Diagnostic Ultrasound System, the high-voltage analog switch circuit is used as a transmitted wave changeover switch circuit between a transmitter and receiver circuit and an ultrasound transducer array including a plurality of ultrasound transducers in the Diagnostic Ultrasound System, or as a changeover switch circuit between the transmitter and receiver circuit and a plurality of probes each including ultrasound transducers in the Diagnostic Ultrasound System to perform switching probe by probe, or as transmitting/receiving separating circuit in the transmitter and receiver circuit. In this case, the transmitter and receiver circuit refers to a circuit that transmits a large voltage-amplitude drive signal for driving the ultrasound transducers and receives a small voltage-amplitude signal based on a reflected wave resulting from irradiation of an ultrasound signal.
In recent years, Diagnostic Ultrasound Systems have been increasingly configured such that a large number of electronics are integrated into a semiconductor integrated circuit device and built into probes, and transmitted wave changeover switch circuits and others have also been increasingly built into the probes.
In a high-voltage analog switch circuit built into a semiconductor integrated circuit device, a high-voltage transistor with a higher withstanding voltage than a high voltage (maximum amplitude value) of a signal supplied to its input and output terminals is used as a switch for transmitting the signal supplied to the input and output terminals. In this case, for performing on-off control of the high-voltage transistor used as a switch, it is necessary to supply the high-voltage transistor with a control signal with a high voltage equal to or higher than a high voltage of a signal to be transmitted. To generate such a high-voltage control signal, a level-shift circuit operating at a high voltage equal to or higher than a high voltage of a signal to be transmitted by the high-voltage transistor as a power-supply voltage may be built into the semiconductor integrated circuit device. Accordingly, a low-voltage control signal is input into the level-shift circuit operating at a high voltage as a power-supply voltage to generate a high-voltage control signal in the level-shift circuit, and the high-voltage control signal is supplied to the high-voltage transistor for on/off control of the high-voltage transistor.
In the case of using a high-voltage analog switch circuit as a transmitted wave changeover switch circuit, a changeover switch circuit for probe-by-probe switching, or transmitting/receiving separating circuit, a drive signal for driving the ultrasound transducers is a large-amplitude signal with an amplitude of about ±100 V at maximum, for example, and therefore, the semiconductor integrated circuit device with the high-voltage analog switch circuit and the level-shift circuit needs to be supplied with voltages of +100 V and −100 V as power-supply voltages for the level-shift circuit. That is, it is necessary to supply the semiconductor integrated circuit device with power-supply voltages with a difference of 200 V therebetween. As such semiconductor integrated circuits with a high-voltage analog switch circuit, semiconductor integrated circuit devices which require power-supply voltages of +100 V and −100 V, +40 V and −160 V, or +200 V and 0 V are known, for example.
PTL 1 describes a semiconductor integrated circuit device with a high-voltage analog switch circuit.
PTL 2 describes a semiconductor integrated circuit device with an analog switch circuit. PTL 2 specifies that voltages of several tens of Volts are supplied as power-supply voltages for a circuit driving the analog switch circuit.